A talk page (also known as a discussion or commenting page) is a page which users can use to discuss improvements to an article or other OpenDevelopment page. When viewing an article (or any other non-talk page), a Discussion option appears in the Actions menu at the top of the page. Click this to switch to the talk page.
The talk page associated with an article is named "Talk:Example", where "Example" is the name of the article. For example, the talk page for discussion of improvements to the article Process is named Talk:Process. Certain pages do not have a Talk page, examples include Special pages like login and watch pages.
To discuss a new topic, click the "New section" tab at the top of most talk pages. Fill out the "Subject/headline" box with a suitable title, preferably not something generic like "Question" or "Problem". A new section can also be started by editing the whole page or an existing section, going to a new line and typing == Heading ==, replacing "Heading" with a suitable title. Place new discussions at the bottom of the page.
To respond to a discussion already in progress, click the "edit" link at the section heading and add your comment below the last entry in the discussion. If you want to respond to a specific comment, you can place your response directly below it. When doing this, keep in mind the advice given below about indentation.
You should sign and date your contributions on all talk pages. To do this easily, type four tildes ~~~~ at the end of your comment, or just click the signature button above the edit box. This will be automatically converted into a user signature and the date and time. (You can change the form of your signature using your User Preferences.)
Indentation is used to keep talk pages readable. Comments are indented to show whether they are replies to other comments, and if so, which ones.
Comments are indented using one or more initial colons (:) or, on some pages, asterisks (*). Generally colons and asterisks should not be mixed. Each colon (or asterisk) represents one level of indentation. You will see these colons (or asterisks) in the wikitext when editing a talk page, but when viewing the page itself you will see the indents.
The first comment in a section will have no colons (or one asterisk) before it. When you reply to a statement, you should use one more colon (or asterisk) than the number that appear in the statement you're replying to. For example, if you're replying to a statement that has 2 colons before it, your response should have 3 colons before it.